Isolating the cause of pump breakdowns
In the second part of his two-part feature, Jamie Casey gets to the root of the problem and outlines the rebuilding process
I was recently asked to repair a slurry tanker which had a recurring problem of passing slurry through the pump when the tanker got full.
The vacuum pump is specifically designed to handle air only, so if slurry makes its way into the pump, it will damage the pump very quickly, leading to an impending overhaul.
Last week, I outlined the steps involved in stripping the vacuum pump and assessing the damage. This week, I look at how to rebuild the pump, as well as figuring out why slurry was making its way into the pump in the first place.
There's not much point in forking out to repair the pump if you don't address the root cause of the problem and fix the float valve of the tanker. This will prevent slurry from making its way down to the vacuum pump and ensure it only handles air - as it was designed to do.
The cost of the overhaul kit (vanes, bearings, seals and gaskets) was €290, and the entire job took approximately five hours. The cost of labour will vary from place to place. However, the pump should be good to go for another four or five years if everything is maintained well - back to filling loads in three minutes and making progress again!
1. After a thorough steam clean of both the body and head of the pump, reassembly can begin.
2. Reinstall the head of the pump. Be sure to replace all gaskets, seals and bearings as you go. These will generally be included in the overhaul kit.
3. Lay the pump on its back to install the front bearing plate and rotor. Ensure the rotor is lifted in square so it doesn’t score the internal surface of the pump as it slides in.
4. With the rotor installed, the new vanes can be fitted in through the rear of the pump. They slide into position in their respective slots in the main rotor.
5. It’s important to remove the lubrication pump from the reservoir prior to bolting the reservoir back into position. Any misalignment in the shafts will end up ruining the lube pump. Once the reservoir is bolted into position, the lube pump can be fitted once again.
6. Add the gearbox oil (80W90) and sufficient lubrication oil (SAE30). The pump is now ready to reinstall and run.
With the top hatch removed from the tanker, it was easy to see the problem — allowing slurry to pass from the barrel into the pump; two of the four fingers surrounding the ball had gotten bent and were jamming the ball tightly in position. With some gentle persuasion, the fingers were bent back into their original position. The ball was now free to slide again, and will float on the rising slurry to seal off the outlet above when the tanker is full.
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